Verizon moves voice with packets

In what will likely be a long migration to an undetermined destination, Verizon Communications Inc. has started using packet switches to carry customer voice traffic in two metropolitan areas.

The use of ATM switching has begun in West Orange, N.J., and Tampa, Fla., where the technology could lead to advanced services but for now represents a way to lower long-term network costs. While the price of the packet gear is comparable to circuit switches, the packet switches use bandwidth more efficiently and require less management.

"This saves money over the long run by reducing network operating costs, using larger interoffice trunks and by using dynamic provisioning," says Phil Harrington, Verizon's voice trunking over ATM (VToA) project manager.

While Verizon is certain it wants packet switching to anchor its networks, the exact technology and the pace of deployment are still unknown.

"This is probably the first time in 30 years that we are going to next-generation switching," Harrington says.

Injecting packet gear for Class 4 tandem switching is just the start, with the eventual goal to use Class 5 packet switches for connecting directly to customers. This will open up an opportunity to sell new, mixed-media services that combine voice, data and video, he says.

"This is a growth vehicle. We'll migrate all our traffic to it over time," Harrington says.

For now, Verizon is content to use ATM as the packet technology, but that could change over time. IP is an alternative that Verizon may use later, but for now IP quality of service (QoS) and circuit management are still immature. ATM offers the QoS guarantees Verizon needs, as well as circuit management features, Harrington says.

The packet-switched VToA application is intended to make call setup more efficient and ease integration of voice, data and video traffic into new services, such as combination voice and text messaging. Verizon and other established local carriers predominantly use circuit switches that set up physical circuits between callers and the parties they are calling.

In West Orange, for example, Verizon is aggregating traffic from 51 end offices where Class 5 switches connect to customers. These end offices used to feed into tandem switches using anywhere from four to 48 individual T-1 trunks. The tandems then connected to other tandems or to other carriers' networks. Competitive local exchange carriers (CLEC) and wireless providers need to connect to Verizon's local network so their customers can complete calls to Verizon customers, and vice versa.

With the Nortel ATM gear, overflow traffic from the same end offices is directed to Nortel MG4000, which takes in the Class 5 time-division-multiplexed traffic and converts it to ATM and passes it along over OC-3c ATM trunks to Nortel Passport 15000 ATM switches. Three of these Passport 15000s are arranged in an OC-12 ring to form a regional core.

The MG4000s become virtual tandems, performing the same function as tandems but using virtual circuits. This enables the use of larger physical trunks - OC-3 rather than T-1 - that contain multiple logical T-1 circuits. With traditional tandems, any trunking changes would require manual provisioning of new T-1s, an expensive and time-consuming process.

"Dynamic provisioning finds the best path for the best results for this call," says Harrington, who adds that the Nortel ATM gear has carried more than 1.8 million voice calls since it went live in February.

One benefit of the new system is that it distributes the switching power to more sites. Rather than having just one Class 4 tandem switch in West Orange, there are three ATM equivalents at different sites in the area. This facilitates faster network recovery and lessens the impact of a switch failure, Harrington says. The closer to customers that the packet technology extends, the more options the carrier has to reroute traffic around problems.

Verizon plans to add more and more MG4000s to migrate all the traffic in the West Orange area to ATM.

"The point is to get it on ATM as soon as possible," Harrington says.

Key to using this equipment is that it blends in with Verizon's existing operations support systems (OSS) software. Nortel already had certification to interoperate with OSSes that were written to Telcordia specifications, so the gear worked with Telcordia-based OSSes Verizon uses. But Verizon also had some non-Telcordia OSSes that required the RBOC to write interfaces to the Nortel equipment, Harrington says.

The Nortel Passport switches will also support IP cards that will enable a transition to IP without replacing an entire chassis, he says. Nortel plans to add significant IP enhancements to the Passport line later this year and into 2003.

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